Separation through crystallization and hydrotropy:

The specificity of hydrotropes in solubilization has been successfully employed for the separation of close-boiling isomeric components from their binary mixtures forming simple eutectics, in some cases even at the eutectic compositions. The purpose of this paper is to propose a novel technique of crystallizing 6-aminopenicillanic acid (6-APA) in a good quality and pure crystalline form from product reaction mixture in a hydrotrope environment. The remaining mother liquor may be used to recover crystalline phenoxyacetic acid (PAA) by dilution with water and subsequently to concentrate hydrotrope solution for recycle. Semibatch crystallization experiments for 6-APA in a 2 l laboratory-scale agitated crystallizer with controlled acid addition from product reaction mixture in hydrotrope solution yield better quality crystalline product than that in absence of hydrotrope. The present study demonstrates the potential efficacy of sodium butyl monoglycol sulphate (NaBMGS) hydrotrope in the separation of 6-APA in pure crystalline form from the product reaction mixture.